With swell (or swell of English swell ) refers to water waves that are out already run out of their forming region; thus swell is the opposite of the wind sea . The totality of all waves from swell and wind sea is called swell .
Order mechanisms have already established themselves in the swell and have contributed to a homogenization of the wave structure (wave height, wave length, period, direction, group formation) (cf. orbital movement ). At the transition from the wind sea to the swell, the wave height decreases and the wave length increases.
If a swell reaches the shallow water area (e.g. the continental shelf / shelf ), the wave bottoms come into contact with the sea floor, i.e. ground contact, and one then speaks of a ground sea . If the ground sea then meets shoals or the shallow surf zone on the coast, the bottom of the wave is slowed down more than the crest of the wave, which then overtakes the wave bottom - the wave breaks. Here we speak of surf .
The strength of the swell depends on the preceding wind sea. The larger the area, the higher the strength, the longer the duration and the more uniform the direction with which the wind acts on the water surface, the more pronounced the resulting wind sea and consequently the swell, which then migrates a few thousand kilometers across the oceans before it turns to surf on a coast.
- Jürgen Gebauer, Egon Krenz: Marine encyclopedia from A-Z . 4th, revised edition, Siegler Verlag, Königswinter 2007, ISBN 978-3-87748-657-3 ; Article: Swell .